The present invention relates to an improved mounting arrangement for a sensing pin in a multicoordinate sensing head of the type which includes a position measuring system for detecting deflection of the sensing pin from a rest position.
A large number of publications relate to multicoordinate sensing heads which are responsive to contact with a workpiece from various directions.
For example, in German DE-AS No. 19 32 010 a multicoordinate sensing head is shown in which the sensing pin is mounted in the interior of a housing by means of a ball joint. Deflection of the sensing pin in an arbitrary direction is transmitted over a special cam follower arrangement which includes a translation cone onto a measuring converter which generates a measuring signal in response to movement of the sensing pin. When the sensing pin is deflected in a direction perpendicular to its axial direction, the sensing pin is swung about the ball joint at an angle with respect to the axial rest position. Such angularly movable sensing pins are unsuitable for some applications. For example, when a sensing pin must be used to measure spatial contours within narrow bores or other internal contours of a workpiece, there may be no room to position a tilted sensing pin as needed.
Another approach known to the art for multicoordinate sensing heads is to mount a sensing pin to a housing such that the sensing pin is deflectable axially as well as in a plane substantially perpendicular to the axial direction. In this approach, the sensing pin is not tilted but rather is shifted radially while remaining parallel to its original orientation. In German patent DE-PS No. 22 42 355 an array of straight guidance systems for mounting the sensing pin to the housing is provided. The approach shown in this patent is relatively expensive to build, since relatively high cost manufacturing techniques must be used to produce straight guidance systems which are dependent on one another and yet which produce required accuracies. Moreover, the system disclosed in this patent utilizes several position-sensitive and direction-sensitive signal generators which operate to form a spatial coordinate measuring system. Such a plurality of signal generators is not always needed for simple measuring tasks on difficult workpiece contours.